Data from: Trait plasticity and tradeoffs shape intraspecific variation in competitive response in a foundation tree species

The ability to tolerate neighboring plants (i.e., degree of competitive response) is a key determinant of plant success in high-competition environments. Plant genotypes adjust their functional trait expression under high levels of competition, which may help explain intraspecific variation in competitive response. However, the relationships between traits and competitive response are not well understood, especially in trees. In this study, we investigated among-genotype associations between tree trait plasticity and competitive response. We manipulated competition intensity in experimental stands of trembling aspen (Populus tremuloides) to address the covariance between competition-induced changes in functional trait expression and aspects of competitive ability at the genotype level. Genotypic variation in the direction and magnitude of functional trait responses, especially those of crown foliar mass, phytochemistry, and leaf physiology, was associated with genotypic variation in competitive response. Traits exhibited distinct plastic responses to competition, with varying degrees of genotypic variation and covariance with other trait responses. The combination of genotypic diversity and covariance among functional traits led to tree responses to competition that were coordinated among traits yet variable among genotypes. Such relationships between tree traits and competitive success have the potential to shape stand-level trait distributions over space and time.耐受邻株的能力（即竞争响应（competitive response）程度）是植物在高竞争环境中取得生存成功的关键决定因素。植物基因型在高竞争压力下会调整其功能性状（functional trait）的表达模式，这或可解释竞争响应的种内变异（intraspecific variation）。然而，学界对性状与竞争响应之间的关联机制尚缺乏充分认知，在树木类群中尤为如此。本研究针对树木性状可塑性（trait plasticity）与竞争响应之间的基因型间关联展开探究。我们通过操控颤杨（Populus tremuloides）实验林分的竞争强度，旨在解析基因型水平上，竞争诱导的功能性状表达变化与竞争能力各维度之间的协变关系。研究发现，功能性状响应的方向与强度存在的基因型变异，尤其是冠层叶生物量、植物化学特性以及叶片生理特性相关性状的变异，与竞争响应的基因型变异显著相关。各类性状对竞争均表现出显著的可塑性响应，且其基因型变异程度以及与其他性状响应的协变关系各不相同。基因型多样性与功能性状间协变关系的共同作用，使得树木对竞争的响应呈现出性状间协同、基因型间却存在差异的特征。树木性状与竞争成功之间的这类关联，有望通过空间与时间尺度上的变化塑造林分水平的性状分布格局。